Conventional electronic tuning devices comprise a pair of identical resonant circuits disposed on a dielectric substrate, each resonant circuit including a conductive elongated film serving as a transmission line and a voltage-controlled capacitive element. The transmission lines of the resonant circuits are arranged in parallel to each other. Microwave energy is coupled with one of the resonant circuits and the tuned signal is then coupled with the other resonant circuit. With this interstage coupling the passband characteristic of the tuning device has a strong peak at the center frequency of the passband with a bandwidth of 20 MHz or less at the -3 dB point from the peak value. Since the bandwidth is inversely proportional to the distance between the two transmission lines, a narrow bandwidth requirement would result in a tuning device having considerable dimensions. For example, the bandwidth requirement of 20 MHz or less is only obtained with a spacing of more than 22 mm or 27 mm at 470 MHz or 770 MHz, respectively.